This invention relates to novel ring-substituted 4-oxo- and 4-thioxo-hexahydro-4H-pyrazino-[2,1-a]isoquinoline derivatives and their preparation. Similar compounds are described in German Offenlegungsschrift No. 1,470,062 and in U.S. Pat. No. application Ser. No. 533,467, now U.S.Pat. No. 4,001,411 granted Jan. 4, 1977.